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POCT ACT and Anti-Xa for ECMO

From Deanna Miller, Point of Care Testing (POCT) Coordinator at Children’s of Alabama:

We have recently merged our extracorporeal membrane oxidation (ECMO) team with the cardiovascular team from the University of Alabama at Birmingham (UAB) and we are doing all pediatric cardiovascular cases at Children’s now. We would like some insight into monitoring coagulation using the activated coagulation time (ACT) and the chromogenic anti-Xa heparin assay.

Deanna and I traded emails on the topic, and it was a pleasure to hear from her, as she is a graduate of UAB’s Medical Technology program and had been a successful student in my hematology and hemostasis classes. Children’s beautiful new facility is right next-door to UAB’s recently built Women’s and Children’s center. Children’s cardiovascular operating room uses the Medtronic HMS Plus, which offers ACTs for both high and moderate-range heparin therapy. Their ECMO service uses both the ACT and the anti-Xa heparin assay, a near-patient test. Although ITC’s Hemochron Signature Elite provides a partial thromboplastin time (PTT), Deanna’s service prefers to continue with the ACT and anti-Xa.

We found an article that addresses correlations among the ACTs from both the Medtronic and the Hemochron and the anti-XaChia S, Van Cott EM, Raffel OC, Jang IK. Comparison of activated clotting times obtained using Hemochron and Medtronic analysers in patients receiving anti-thrombin therapy during cardiac catheterization. Thromb Haemost 2009;101: 535-40.

Deanna also asked for an expert in heparin management of neonates and peds during ECMOJohn Olson, MD, PhD, Professor, Vice Chair for Clinical Affairs, University of Texas Health Sciences Center in San Antonio, provided a referral, however, if you know of someone with experience, please send a referral to [email protected] and I will be sure Deanna receives your message.

Comments (2)
Anticoagulant Therapy
Jul 3, 2013 11:02am

The anti-Xa assay is the best option for unfractionated hepa
The anti-Xa assay is the best option for unfractionated heparin monitoring in pediatric ECMO (however some experts suggest both APTT and anti-Xa assay for monitoring in this setting), but it still have several limitations:
1. All assays (with or without exogenously added antithrombin) depend on endogenous antithrombin level, and heparin concentration would be underestimated if patient’s AT level is around 40-60% (typical initial values in newborns on ECMO);
2. Elevated level of free hemoglobin and hyperbilirubinemia are often observed in pediatric ECMO and could interfere with chromogenic assay leading to underestimation or overestimation of heparin activity in the sample; and sometimes it is impossible to measure anti-Xa activity in extremely hemolysed plasma samples.

Jul 3, 2013 10:45am

Several comments: POCT ACT has a very good correlation with
Several comments: POCT ACT has a very good correlation with anti-Xa or heparin dose only in supratherapeutic heparin concentration (i.e. >0.6-0.7 IU/ml); in typical target level for ECMO (0.3-0.7 IU/ml) this corralation is poor or absent. Recent paper confirms it and even POCT APTT is not as good as laboratory APTT assay:

Maul TM, et al. Activated partial thromboplastin time is a better trending tool in pediatric extracorporeal membrane oxygenation.Pediatr Crit Care Med. 2012 Nov;13(6):e363-71.

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